As a unit for connecting electromagnetic contactors to each other, a switch unit described in Patent Document 1 is known. In the switch unit, by fitting a connection changeover portion in slits in connection-side side surfaces of two juxtaposed switches, when one of the switches is brought into a turned-on state, the transition of the other switch to the turned-on state is prevented. In addition, there are provided E-shaped clamps each of which has a central shaft and a pair of leg portions sandwiching the central shaft, and there are formed ribs having concave portions in opposing surfaces formed at end portions of the connection-side side surfaces of the two switches. Each of the clamps is attached from the outside such that the central shaft is fitted in the concave portion and the leg portions hold the rib between them from a side opposite to the side of the concave portion of the rib, and the two switches are thereby integrated.    Patent Document 1: Japanese Translation of PCT Application No. 2000-502208